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A Scientific Assessment of a New Technology Orbital Telescope (1995) / Chapter Skim
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6 ISSUES AND CONCERNS
Pages 60-64

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From page 60...
... NEED FOR FULL SYSTEMS ANALYSIS In the course of its briefings from BMDO, Lockheed, Itek, and Charles Stark Draper Laboratories, the task group identified areas where there are clearly open or, as yet, undefined issues that could significantly affect the ATD/NTOT's performance of astronomical observations or valid demonstration of technology for future scientific applications. At present the ATD/NTOT is a collection of components that exist in one form or another in various parts of the relevant industries.
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From page 61...
... More importantly, however, guide stars will be significantly less abundant than assumed, especially at higher galactic latitudes. The source of the average stellar density data presented in the Lockheed/Itek briefing is not known to the task group, but the briefing assumed an average guide-star density of about 25 per square milliradian at a limiting magnitude of 19.
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From page 62...
... These elements provide flat specular surfaces facing the primary obscuration that permit photons to enter the focal plane area by direct reflection or by other paths through the optics. Because the dynamic range of brightness is so large between the Sun and Moon, on the one hand, and deepspace objects, on the other, scattered light can be a tremendous problem for any studies of faint objects, that is, for the prime astronomical targets of the ATD/NTOT.
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From page 63...
... Lessons learned from Clementine about software development include the following: i · Take care to understand the impact of the software development environment on test and schedule; · Realize that "non-commercial" processors are not supported as well as commercial ones; · Assure that undefined processor states cannot enable critical circuitry; and · Make maximum use of software verification tools prior to new uploads to the spacecraft. IMAGING DETECTORS IN A HIGH-RADIATION ENVIRONMENT A problem inherent in imaging arrays is their susceptibility to radiation events, often called cosmic rays.
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From page 64...
... The feasibility of this test will depend on additional study of the extent to which cosmic-ray events can be handled, either by reducing them through shielding of the chip (although at least one side cannot ever be shielded) , by finding intelligent ways to analyze data contaminated with such events, or by implementing continuing improvements in CCD technology.
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Key Terms

  • scattered light
  • control loop
  • astronomical operations
  • guide star
  • astronomy operations

  • faint objects
  • dynamic range
  • software development
  • stellar density
  • molniya orbit

  • astronomical observations
  • controlling pitch
  • wavefront sensor
  • galactic center
  • figure correction

  • density falls
  • characteristically require
  • finding intelligent
  • achieving timely
  • finding guide

  • hemisphere facing
  • total exposure
  • assumed success
  • implementing continuing
  • installing baffles

  • illuminated ccds
  • processor states
  • faint moving
  • tripodal truss
  • time scale


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